The innovative use of oligonucleotide colloidal gold nanoparticle conjugates is proposed as a simple, rapid and inexpensive method for the detection of Polymerase Chain Reaction (PCR) amplified nucleic acids of the I1307K mutation of the APC gene. The APC gene is known to play an important role in colorectal cancer (CRC). To date, only sequencing, which requires two days of processing and is very expensive, has been utilized for screening. Preliminary examination of this new class of hybridization probes in conjunction with single stranded synthetic oligonucleotide targets already has demonstrated the potential of this approach for the detection of a model synthetic target sequence. Specifically, single base imperfections, regardless of position along the target strand, can be differentiated easily from a perfect target sequence using this novel colorimetric technique. This detection strategy is based on the aggregation of colloidal gold particles which leads to changes in the particle surface plasmon band. We propose to further develop this method in order to generate a rugged and routine technique for analysis of the PCR products of the I307K APC gene mutation. This would provide the first molecular probe based assay for screening of this important cancer gene. PROPOSED COMMERCIAL APPLICATIONS: A faster, simpler assay for screening mutations of the APC gene would facilitate early diagnosis of this deadly disease.